1. Field of the Invention
Embodiments of the present invention generally relate to electronic device manufacturing and more particularly to methods and apparatus for preventing plasma leakage around a plasma processing chamber isolation valve.
2. Description of the Related Art
A substrate processing chamber typically communicates with a substrate transfer chamber through a sealable opening that is both wide and relatively short to accommodate insertion and removal of horizontally-oriented substrates. It is known to use a chamber isolation valve, also known as a slit valve, to seal such an opening. For example, a sealing plate, also known as a door, of the chamber isolation valve may be extended to seal the opening, and retracted to permit passage of substrates through the opening. Chamber isolation valve designs that avoid the problems of (1) particle generation through rubbing friction and/or repeated metal-to-metal contact during operation, and (2) uneven compression of resilient sealing elements, are preferred.
As substrate processing chambers increase in size and the required plasma power for plasma-processing substrates exceeds 10 kW, complete containment of plasma in such chambers has become problematic. Ordinarily, electrically grounded conductive surfaces, e.g., the metallic chamber walls, substantially contain the plasma present in a PVD, PECVD or other plasma processing chambers during substrate processing. In some instances, however, plasma leakage has occurred from processing chambers, escaping past the closed isolation valve door and into adjacent chambers. This is particularly true for chambers processing very large substrates, i.e., larger than about 1,000 mm×1,000 mm.
Accordingly, a need exists for improved methods and apparatus for grounding a chamber isolation valve to prevent plasma leakage past the isolation valve while avoiding metal-to-metal contact between components of the isolation valve and its associated sealing surfaces. The improved methods and apparatus should be applicable for isolation valves operating against large pressure differentials between chambers.